Dear LF Group,
I recorded spectrograms around 137.79kHz, between about 1500 and 1900 on
1st December, but no identifiable signals. The part of spectrum ZL6QH was
operating in seems pretty clear here apart from the lines straddling
137.790kHz, so would suggest moving down about 0.2Hz for future tests.
Congratulations on W4DEX's reception of ZL6QH; I imagine this must be the
new distance record on the band.
I transmitted on 72.4018kHz from about 2330 until 0700 over the night of
1/2 December - thanks for the reports; I will try to get QRV a bit earlier
if possible next time I run the beacon.
I worked through the FS figures I measured last week on 73k - it comes out
like this:
G3AQC 130mW ERP
G3LDO 85mW ERP
M0BMU 100mW ERP
Rugby 73.25kHz 7.5kW ERP
Bearing in mind that for all the signals apart from my own, deviation of up
to +/-3dB could be expected due to relying on only one field strength
measurement, and that I have not attempted to include ground wave losses.
So amateur signals are roughly 50dB down compared to the Rugby FSK signal.
If the receiver is using about 0.01Hz bandwidth to obtain a few dB SNR (ie
a visible QRSS signal), then the FSK should have at least 6dB SNR in 300Hz
BW, so be an easily audible signal.
Cheers, Jim Moritz
73 de M0BMU
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